1. Field of the Invention
The present invention relates to a method of flushing a nozzle of an inkjet recording head of an inkjet recording apparatus that ejects droplets of an ink containing a pigment toward a recording medium to record an image thereon, by ejecting, from the nozzle, droplets of the ink to recover an ink-ejection performance of the nozzle.
2. Discussion of Related Art
A conventional inkjet recording apparatus has such a problem that a nozzle of an inkjet recording head thereof may fail to eject normally droplets of ink because the ink dries around a nozzle-opening surface of the head or a viscosity of the ink increases in a low-temperature environment, i.e., because energy needed to eject the ink droplets increases because of the increased viscosity resistance. To solve this problem, Japanese Patent Document No. 6-39163, for example, proposes to carry out a maintenance operation, i.e., a flushing operation of removing, from a nozzle, bad ink having increased viscosity so as to recover an ink-ejection performance of the nozzle. More specifically explained, the flushing operation includes (a) moving, based on a time measured by a timer, or upon reception of a command signal, the inkjet recording head to a waste-ink collecting portion and (b) operating the head to attempt to eject a predetermined number of ink droplets.
Meanwhile, two sorts of inks, i.e., a dye ink and a pigment ink may be used in an inkjet recording apparatus. The dye ink contains a solvent and a dye dissolved in the solvent, and enjoys a good color development and a fine hue expression. Therefore, the dye ink can be used to record, e.g., photographs with high quality. However, in the case where the dye ink is used with plain paper, it may bleed. On the other hand, the pigment ink contains a color material that is not dissolved in a liquid but is dispersed therein. Thus, the pigment ink enjoys a high water resistance and does not bleed into plain paper. In particular, in the case where a black pigment ink is used, the black ink enjoys an increased degree of density and accordingly a black image recorded with the black ink enjoys a high degree of clarity. Thus, there have been proposals that an inkjet recording apparatus record images with higher quality by using a pigment ink as a black ink in combination with one or more dye inks as one or more color inks, or using pigment inks only.